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Mapping electrical system

Mapping electrical system

#1
05-07-03, 10:28 AM
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Join Date: Apr 2003
Location: USA
Posts: 104
Mapping electrical system

I'm in the process of mapping the electrical system in the house my wife and I recenlty purchased. I'm not having any trouble with the basics of mapping it out, and calculating wattage on each circuit. What I am wondering is: If there are recepticles on a circuit that don't normally have anything plugged into them ( used mainly for temporary items, such as a vaccuum), is there a standard rule of thumb regarding the number of watts that should be "allocated" to these recepticles when calculating the load on the circuit (to determine how many recepticles should be allowed on one circuit)?

#2
05-07-03, 10:42 AM
texsparky
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Not in residential. In commercial, it is 180 watts per outlet. Residential is basically calculated at 3 watts per sq.ft for the General lighting and receptacle loads.

ie. 1500 sq. ft x 3 watts per sq.ft. =4500 watts

4500 divided by 120 volts = 37.5 amps = (2) 20 amp circuits or (3) 15 amp circuits

#3
05-07-03, 10:57 AM
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Join Date: Apr 2003
Location: USA
Posts: 104
Thanks, that helps a lot!

Next question (because I don't think there's really a code regulation on this, but I could be wrong): From the Sherlock Holmes work I've done, so far, I know that the dining room light, three bedroom lights, an outside porch light, and a bathroom light are all run on one circuit. I'm going to pull new wire to the bathroom to install outlets (the bathroom has ZERO outlets at this point!), so it'll be on it's own circuit. I had planned on also tieing the bathroom light into this circuit, as well.
(Running from panel to light, to GCFI outlet, to second outlet)

From a practical standpoint, does it make sense to leave all of the bedroom, dining room, and porch lights on this same circuit, or should I split this (I'm going to be re-wiring, anyway, because the old non-grounded wire is in pretty bad shape) into a couple of circuits (or is this simply dependant on the calculation of watts/amps on the line, discussed in the previous posts)?

#4
05-07-03, 01:59 PM
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Join Date: Feb 2002
Location: port chester n y
Posts: 1,983
How do you cool your house? Central AC or window AC units?

#5
05-07-03, 02:00 PM
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Join Date: Apr 2003
Location: USA
Posts: 104
Central AC, why?

#6
05-07-03, 08:36 PM
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Location: United States
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Received 1 Upvote on 1 Post
Lighting is a relatively small load. You can put a lot of it on one circuit without problems.

180-watts per duplex receptacle is still a good rule of thumb in residential. In commercial, it's mandatory to use this number, but in residential it is still a good rough planning number.